The majority of passenger car and light-duty trucks, especially in North America, operate using port-fuel injection (PFI) engines. In PFI engines, the fuel is injected onto the intake valves and then pulled into the combustion chamber during the intake stroke. Components of the fuel are unstable in this environment and form deposits on the upstream face of the intake valve. These deposits have been found to affect a vehicle’s drivability, emissions and engine performance. Therefore, it is critical for the gasoline to be blended with additives containing detergents capable of removing the harmful intake valve deposits (IVDs).
Established standards are available to measure the propensity of IVD formation, for example the ASTM D6201 engine test and ASTM D5500 vehicle test. However, rigorous testing conducted in a modern fleet of vehicles in a statistically robust design can provide greater insight into the actual performance of modern PFI engines with available gasoline additive packages. In this study, an optimized mileage accumulation protocol was used to assess the performance of new experimental gasoline additive packages in removing the IVDs in a fleet of vehicles typical of engines and vehicles available in the North American vehicle parc. The performance of a gasoline additive package, both at lower and higher additive treat-rates, was compared to that of a commercial additive package at EPA-approved lowest additive concentration (LAC).
Based on three decades of expertise, the testing protocol was optimized to use fewer vehicles and shorter mileage accumulation than previously required for the same statistical confidence. It was observed that the tested experimental gasoline additive packages demonstrated a statistically higher cleanup at both treat-rates compared to the commercial LAC additive package. This rigorous statistically-robust test protocol can be used to assess candidate fuel additive packages for the North American gasoline market.